In the manufacture of corrugated paperboard, paper sheets are bonded with an adhesive to opposite faces of a corrugated core, and the laminated sheet is then passed through a slitter which slits the sheets into a series of strips of various predetermined widths. The slit strips are then passed through cut-off knives which cut the slit strip into lengths. As it is often desired to cut the strips into different lengths, multiple cut-off units are used, with certain of the strips being directed to one cut-off knife, and other groups of strips being directed to a second cut-off knife.
Following the cutting of the strips, the cut lengths or sections are conveyed to a stacking mechanism, as described in U.S. Pat. No. 3,905,595, which serves to stack the cut sections and convey the stacks to a given site.
It is important that the cut sections be maintained in proper machine direction orientation on the conveyor approaching the stacking machine, for if the cut sections are skewed, interleaving of the sections will occur during the stacking with the result that the stacks cannot be properly separated from one another.
Attempts have been made in the past to prevent skewing or misalignment of the cut sections on the conveyor leading to the stacking machine. In the past, canvas drapes have been employed which were adapted to ride on the cut sections in an attempt to prevent skewing. However, the draped canvas would not correct skewing which may have occurred at the cut-off knife and would, at most, control skewing on the conveyor. Furthermore, the use of the draped canvas had certain distinct disadvantages in that after a period of use the canvas became ragged or worn, and the draped canvas also restricted access to the conveyor in the event of a jam-up.
Attempts have also been made in the past to control skewing of the cut sections on the conveyor by use of sandwich belts in which the cut sections were held between the cooperating endless belts. The use of the cooperating belts, at most, controlled skewing on the conveyor and did not correct skewing which had occurred at the cut-off knives. Furthermore, the gap or spacing between the cooperating belts was set for a given thickness of paperboard, and during normal daily operation, it was common for various thicknesses of paperboard to be run through the machine. With the gap set for the thickest paperboard, the unit would not give proper control when running paperboard of lesser thickness.
Pivoted floation rolls have also been used in the past in an attempt to control skewing on the conveyors. In this type of system, one or more transverse rolls were mounted to ride against the upper surfaces of the cut sections and the resulting pressure would provide some measure of control against skewing. However, the use of the pivoted flotation rolls would not correct skewing which had occurred at the cut-off knife. Moreover, if the cut sections were located only along one side edge of the conveyor, the flotation roll would tend to tilt, with the result that a differential in pressure would be applied transversely across the cut sections, causing the sections to skew, so that under certain conditions, the flotation rolls accentuated, rather than controlled skewing.